As an information-recording medium for recording data, optical disks such as a CD (Compact Disc) and a DVD (Digital-Versatile Disc) have captured attention, and as an information-recording apparatus for recording data into the optical disk and as an information-reproducing apparatus for reproducing data from the optical disk, the optical-disk apparatus has proliferated.
There are such recordable CDs as CD-R and CD-RW, while there are such recordable DVDs as DVD−R, DVD+R, DVD−RW, DVD+RW and DVD-RAM. Then, data are recorded to and reproduced from the respective media according to the corresponding standards which are predetermined.
Of such information-recording media as described above, in a rewritable information-recording medium, defect management is applied conventionally as a way of maintaining the reliability of recorded data. In such defect management as described above, a list associating a defective portion of the recording medium with an area to be used in lieu of this defective portion is stored in a predetermined sparing area of the information-recording medium so that the list as described above is referred to at a subsequent time of recording and reproducing information, thus controlling so as to avoid the use of the defective portion.
Next, a method of replacing a defective area according to the defect management is briefly described. Two types of replacing of the defective area in the defect management, slip sparing and linear sparing, are generally used. In the slip sparing, when a defective area is detected, an area subsequent to the defective area is used in lieu of the defective area. Then, when the slip sparing takes place, a logical address associated with data and a physical address indicating a position of the area are to respectively slip by 1. In the linear sparing, when a defective area is detected, a sparing area secured in advance at a location physically remote from the defective area is used. It is noted that, in the linear sparing, as the subject of replacing is located physically remote from the defective area, it may take longer to access relative to the slip sparing. For instance, in the DVD-RAM, the slip sparing is applied to a defect (an initial or primary defect) detected in an initializing process (a formatting process) of the disk, while the linear sparing is applied to a defect (a secondary defect) detected during recording of user data after the initializing process. In other words, in the DVD-RAM, both the slip sparing and the linear sparing are used. Then, defect information on the initial defects is registered in a Primary Defect List, “PDL”), while defect information on the secondary defects is registered in a Secondary Defect List, “SDL”). In the DVD+RW, only the linear sparing is applied.
In the DVD+RW standard and the DVD-RAM standard, the user can request to record data per sector. However, when actually recording into the optical disk, the recording is done per a recording block of a predetermined size, called an ECC block. Now, the ECC block is composed from a user-data area consisting of 16 sectors. Therefore, when there is a request from a user to record on a sector-by-sector basis, a process is performed such that data of the ECC block that occupy recorded sectors requested are first read out from the optical disk after which the occupying data are overwritten with the data requested to be recorded so as to write back data on a recorded-block by recorded-block basis. This is called a Read-Modify-Write process.
In the DVD-RAM and the DVD+RW, for a secondary defect (the defect during the recording of the user data), data sparing is performed per ECC block. Therefore, a sparing list for managing defects also exists per ECC block. In other words, even when only some sectors within the ECC block have defects, all data of the ECC block are replaced. This is because, in the DVD, as data-error correcting is typically performed per ECC block, there is a high likelihood that, when there is a defective sector within the ECC block, data of other sectors within the ECC block cannot be read out.
Thus, in the Read-Modify-Write process as described above, there is an inconvenience that, when an error takes place at the time of reading out the ECC block so that the data of the ECC block cannot be read out, as not all of the data within the ECC block are being maintained, the ECC block cannot be replaced. Even when only data of sectors for which there is a request from a user for recording are replaced, there can be no choice but to record dummy data in a sector other than recorded sectors requested, for the ECC block for which such data are replaced. When there is a request from a user to reproduce a sector in which dummy data are recorded, erroneous data are returned to the user.
When trying to provide for a sparing list on a sector-by-sector basis, for example, in order to deal with such inconvenience as described above, a sparing list having a size 16 times (1 ECC block=16 sectors) relative to a conventional method for managing defect per ECC block is required, also requiring a large-sized memory capacity for maintaining the defect-management information. Moreover, as described above, when there is a defective sector within the ECC block, as there is a high likelihood that data of other sectors within the ECC block also cannot be read out, replacing is eventually performed per ECC block so that, taking into account the memory capacity, etc., there are more disadvantages than advantages in maintaining a defect list on a sector-by-sector basis.
Now, an apparatus is proposed that takes into account whether there is data sparing so as to manage defects in an information-recording medium (refer to Patent Document 1, for example.) The apparatus disclosed in the Patent Document 1 is an apparatus that sets, when replacing a defective area, flag information indicating whether data are replaced so that the flag information is referred to when reproducing such that, when reproducing area in which data are not replaced is requested, a corresponding defective area is reproduced. However, even with this apparatus, when there is a request for recording on a sector-by-sector basis but the ECC block including the sectors requested for recording cannot be read out, the requested data cannot be replaced.
Patent Document 1    JP2000-322835A